blob: 16f3a9dd9f06277cfb3e97048be60d16dde0f5a9 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
|
{- making the Annex monad available across threads
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Assistant.ThreadedMonad where
import Common.Annex
import qualified Annex
import Control.Concurrent
import Data.Tuple
import System.Posix.Types
{- The Annex state is stored in a MVar, so that threaded actions can access
- it. -}
type ThreadState = MVar Annex.AnnexState
{- Stores the Annex state in a MVar.
-
- Once the action is finished, retrieves the state from the MVar.
-}
withThreadState :: (ThreadState -> Annex a) -> Annex a
withThreadState a = do
state <- Annex.getState id
mvar <- liftIO $ newMVar state
r <- a mvar
newstate <- liftIO $ takeMVar mvar
Annex.changeState (const newstate)
return r
{- Runs an Annex action, using the state from the MVar.
-
- This serializes calls by threads; only one thread can run in Annex at a
- time. -}
runThreadState :: ThreadState -> Annex a -> IO a
runThreadState mvar a = modifyMVar mvar $ \state -> swap <$> Annex.run state a
{- Runs an Annex action in a separate process, using a copy of the state
- from the MVar.
-
- It's up to the action to perform any necessary shutdown tasks in order
- for state to not be lost. And it's up to the caller to resynchronise
- with any changes the action makes to eg, the git-annex branch.
-}
unsafeForkProcessThreadState :: ThreadState -> Annex a -> IO ProcessID
unsafeForkProcessThreadState mvar a = do
state <- readMVar mvar
forkProcess $ void $ Annex.eval state a
|
